a) Field of the invention
The invention is directed to a diaphragm bellows device comprising a diaphragm bellows with a plurality of successive diaphragms which are welded together at the outer and inner edges, wherein the diaphragm bellows can be adjusted in length between an expanded state and a contracted state, and comprising a protective device surrounding the successive diaphragms.
b) Description of the Related Art
Diaphragm bellows of the type mentioned above, which are used particularly as vacuum leadthroughs, are known in various embodiment forms. For example, these diaphragm bellows are used for sealing actuating stems or spindles inside a housing of a vacuum valve. Diaphragm bellows are adjustable in length between a contracted state and an expanded state. Normally, the device in connection with which the diaphragm bellows is used has a limit for the expansion of the diaphragm bellows which predetermines the completely expanded state of the diaphragm bellows. The maximum length of the diaphragm bellows in its fully expanded state is usually also specified by the manufacturer.
In diaphragm bellows of this kind, when foreign bodies fall into the intermediate spaces located between two adjacent diaphragms at the outer side of the diaphragm bellows and are trapped there, this could damage the diaphragm bellows when contracted, possibly after repeated expansion and contraction processes, so that the diaphragm bellows are no longer tight. Diaphragm bellows are used, for example, in transfer valves arranged between two vacuum chambers and frequently lie below the valve opening in the installed state. When a wafer breaks while moving through the valve opening, splinters or fragment s of this wafer can fall between the diaphragms and be trapped in the gaps between the diaphragms.
For this reason, it has already been suggested to protect the diaphragm bellows by surrounding it with a self-supporting, telescoping sleeve. This is disadvantageous particularly in that particles are generated and released in to the vacuum when the telescoping parts of the sleeve are displaced relative to one another. Also, these telescoping sleeves have a relatively large installed length which can increase space requirements.
An important object of the invention is to provide a diaphragm bellows device in which the diaphragm bellows is protected against the penetration of parts into the gaps between two adjacent diaphragms so that additional particles are prevented as far as possible from being released into the vacuum when the diaphragm bellows are adjusted. Another object of the invention is to provide a diaphragm bellows device which is simple to produce and assemble and in which the diaphragm bellows are protected against penetration and release of foreign bodies between the adjacent diaphragms.
According to the invention, this object is met by a diaphragm bellows device which comprises:
a diaphragm bellows with a plurality of successive diaphragms which are alternately welded together at the outer and inner edges, wherein the length of the diaphragm bellows can be adjusted between an expanded state and a contracted state, and
a plurality of sleeve parts which surround the successive diaphragms and which, together, enclose the successive diaphragms in the expanded state of the diaphragm bellows over its entire longitudinal extension and overlap to a greater or lesser extent in axial direction of the diaphragm bellows depending on the adjusted length of the diaphragm bellows,
wherein at least one of the sleeve parts is held on the welded outer edges of two adjoining diaphragms by means of a snap connection.
No other separate guide device is required for the at least one sleeve part that is held on the outer edges of two adjacent diaphragms. During the length adjustment of the diaphragm bellows, this sleeve part is carried along by the movement of the diaphragms themselves.
In an advantageous embodiment form of the invention, the diaphragms at the ends are welded to end pieces by which the diaphragm bellows can be connected to other parts. In this way, for example, a vacuum-tight connection with a vacuum chamber or a part of a vacuum valve can be produced. Insofar as end pieces of this kind are provided, diaphragm bellows is understood in the present Application to mean the unit comprising the successive diaphragms with the end pieces welded to both ends. In principle, it would also be conceivable and possible to connect, particularly to weld, the end diaphragms on one or both sides directly to a part of the vacuum device, for example, to a part of a vacuum valve.
In a preferred embodiment form of the invention, an end piece sleeve part is fastened to the two end pieces of the diaphragm bellows and extends from this end piece in the direction of the other end piece. The end piece sleeve parts and the one or more sleeve parts fastened to the outer edges of two adjacent diaphragms also overlap somewhat in axial direction in the expanded state of the diaphragm bellows. The sleeve parts that are individually fastened to the end pieces and to the diaphragms are advantageously spaced apart somewhat in radial direction and therefore do not contact one another. Due to this fact that the individual sleeve parts are arranged without contacting and, accordingly, without friction, practically no additional particles are generated during the contraction and expansion of the diaphragm bellows.
In an advantageous embodiment form of the invention, each of the one or more sleeve parts held at the outer edges of two adjoining diaphragms has a jacket and a web which projects inward therefrom and which is provided with a groove-shaped recess at its inner end side in order to clip the sleeve part to the outer edges of the two adjoining diaphragms.
The various features and constructions according to the invention are set forth in the claims.